WHY WON'T MY CAR START?

my car has been running fine, but a week or so ago it wouldn't start for a long time(like 15 minutes) but when I went back an hour or so later it was fine. So yesterday while I was driving it seemed to cut out on me once or twice while accelerating. Now when I try to start the car it will turn over like it wants to start but yet, it will not. It is not making any unusual noises while it is turning over. Fuel pressure seems fine, although when I pull the pressure regulator output hose there is a stream of fuel while cranking(not sure if this is normal or not). There is spark at the plug.
Wondering if it might be the timing belt, but like I said, there is not any unusual noise-i would thing the valves would make a noise if it were the timing belt.

Well, I replaced the fuel pressure regulator and the car still won't start-seems like a fuel problem more than anything else-sounds like I have compression, but still won't catch and turn over-any other ideas?